How hard will it be to get into the Marines with a bad knee?

When I was younger I had a problem with my knee dislocating when I would pivot on turf playing sports. I have recently decided that the Marines would be a great opportunity for me. I want to give back to this country and fight for our freedom.This is something I wan very much and I will do anything to have the honor of being part of the United States Marine Corps. I was hoping someone could help me out and give me any suggestions on what I can do to make this possible.